1. Field of the Invention
The present invention relates to a method and an apparatus for controlling a screening device which serves for screening exterior light illuminating a room from the outside. In particular, the invention relates to a method and an apparatus for controlling blinds or shutters of a room.
2. Description of the Related Art
Blinds or shutters serve on the one hand to prevent dazzling in the case of direct incidence of sunlight or in general in the case of strong exterior lighting, so that even in the vicinity of windows is possible to work without being dazzled. Further, in the case of direct incidence of sunlight, blinds prevent a too strong heating of the room.
Because of the increasing prevalence of work with computer screens in particular the factor of dazzle-free working is of great significance. For this reason, as is known, the blinds of a room are often closed immediately upon a first occurrence of dazzling. Then, as a rule, the blinds remain closed for the whole day, so that for the whole day artificial light is needed for illuminating the room. There was thus developed a method, described in EP 94 119 424, for setting the total light in a room, and an apparatus for carrying out this method, with which energy consumption can be minimized. In accordance with EP 94 119 424, not only is the interior lighting of the room dimmed in dependence upon the level of natural lighting, but also a screening device of the room, such as e.g. a blind, is controlled in dependence upon the natural light in accordance with predefined control functions, so that the natural light is automatically dimmed by means of the screening device. There was thus realised a blind control which on the one hand permitted an extensive exploitation of the natural light and on the other end provided always for dazzle-free working.
This blind control does not, however, take into account factors relating to climate. Through windows and blinds there occurs, however, a considerable temperature exchange with the environment, which by means of the setting of the blinds can be controlled within certain limits. Thus, by closing the blinds, for example a warming up of the room through the incidence of sunlight, or a cooling during the night, can be reduced. If the blind control were now configured only with regard to these factors, the energy consumption for the heating/cooling of the room could be correspondingly reduced and the comfort for a person present in the room could be increased. On the other hand, such a kind of blind control cannot ensure that working in the room is always dazzle-free.